Determination of Drying Constants of Some Selected Roots and Tubers

1. International Journal of Trend in Scientific Research and Development (IJTSRD) Volume: 3 | Issue: 4 | May-Jun 2019 Available Online: www.ijtsrd.com e-ISSN: 2456 - 6470 Determination of Drying Constants of Some Selected Roots and Tubers Orua Antia1, Innocent Oboh2, William Olosunde1 1Department of Agricultural and Food Engineering, 2Department of Chemical Engineering 1,2University of Uyo, Uyo, Akwa Ibom, Nigeria How to cite this paper: Orua Antia | Innocent Oboh | William Olosunde "Determination of Drying Constants of Some Selected Roots and Tubers" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456- 6470, Volume-3 | Issue-4, June 2019, pp.717-722, URL: https://www.ijtsrd.c om/papers/ijtsrd23 916.pdf Copyright © 2019 by author(s) and International Journal of Trend in Scientific Research and Development Journal. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0) (http://creativecommons.org/licenses/ by/4.0) This allows for safe storage over a long period of time, reduction in weight and volume hence minimize packages, transportation cost and storage (Doymaz, 2007). Various models have been proposed by researchers, in an attempt to obtain drying rate constant for use in predicting the time of drying to obtain any desired moisture content of the material (Hazarika and Datta, 2014; Uwem et al., 2018 ). However, in some cases of drying, there is fluctuation in the temperature of the heat source. For example, sun drying is the major available method of drying for local farmers with no capital to purchase drying equipment or no electricity in their operational environments. Hence, the time of drying becomes inconsistent to be used for predicting or monitoring the drying time to obtain any desired moisture content of a material subjected to drying. Therefore, the mass of the material could be the only dependent variable to be used to predict when to stop drying to obtain the desired moisture content. In this circumstance, it is necessary to have a data bank of various drying constants of materials rather than their drying rate constants. These values of drying constants when employed in an established model would be used to predict mass vis-a-vis time to stop drying of such material in order to obtain the desired moisture content irrespective of the drying conditions (Antia et al., 2014). It is necessary to emphasize that drying constant is not the same as drying rate constant as the latter is in terms ABSTRACT In an attempt to easily determine the desired moisture content at any time (t), of selected freshly harvested roots and tubers (yellow cassava, carrot, cocoyam and yam) of economic importance subjected to drying under unsteady temperature conditions such as sun drying, especially in the rural areas where there is no electricity or funds availability to acquire suitable drying equipment by local farmers; the drying constants based on established model that is anchored on mass of the material at any time t was carried out. In this study, three mass classifications, namely: small, medium and large were prepared for each material and subjected to oven drying at a given temperature till bone dry mass. The experimental values obtained were computed and graphs plotted to obtain the slopes as drying constants of values 0.3114, 0.1092, 0.3736 and 0.3790 for bulk samples of yellow cassava, carrot, cocoyam and yam respectively. Keywords: Yellow cassava, Carrot, Cocoyam, Yam, Drying constants INTRODUCTION Drying is a term used to describe the removal of water from material. Drying may be affected by temperature, size of material, time of exposure of material and nature of the material, etc (Antia et al., 2019). Temperature and time seems to be a major controlling factor especially when conventional dryers are employed. The major reason for drying agricultural products is to facilitate the reduction in moisture content. IJTSRD23916 of time while the former is in terms of mass changes at any time (t) undergone by the material with respect to its initial mass when the material is freshly harvested. In this study, some selected roots and tubers commonly grown in Nigeria and are of immense economic importance; hence require preservation by the local farmers who in some cases have no modern drying sources, non-availability of capital for acquiring drying equipment and no steady source of heat, etc were used. The selected roots and tubers in this research work are carrot, yam, cassava and cocoyam. Carrot (Daucus carota subsp. sativus) could exist in colours such as orange, purple, red, white, black and yellow (Sifferlin and Aloyanders, 2018). It is a source of beta carotene, vitamin A, potassium and cholesterol lowering pectin, vitamin B6, vitamin C, folic acid, thiamine and magnesium. Doymaz (2004) worked on convective drying of carrot and observed that the moisture diffusivity increases with increase in temperature. Hosain et al. (2012) employed thin layer experiment to determine the layer drying characteristics and energy consumption of carrot slice in a microwave dryer. Yam is in the family of Dioscoreacea of the genus Dioscorea (Uyigue and Achadu, 2018). It is one of the primary sources @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 717

2. International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470 of food energy in Nigeria. Drying would ensure the reduction of moisture content of the yam and so would inhibit microorganism growth among other benefits. Cassava (Manihot esculenta) is edible woody shrub with large roots. In Africa, it has increase significance because of its diverse uses, affordability, tolerance to environmental stresses and high productivity where other crops fail. There are many varieties of cassava. The ordinary varieties are generally white while yellow flesh is another variety. However, these varieties have similar characteristics. Drying provides a solution to maintain the quality of the tuber, improve the storability of the products and reduced the cyanogenic glucoside content (Westby, 2002). A study by Agiriga and Iwe (2018) on drying rate of selected varieties of shredded cassava at various times of harvest using motorized shredder recommend that a combination of parameters such as harvesting time, shred diameter, drying time (second) and temperature prevent quick spoilage and quicken drying of cassava shreds. Cocoyam (Colocasia esclutenta) belongs to Araceae family (Akanbi et al., 2004). They are source of dietary carbohydrate. It is relatively high in protein, fat, vitamins (vitamim A and C, thiamine, calcium, niacins, iron, phosphorus and mineral (Ihekoronye and Ngoddy, 1985). Cocoyam contains digestible starch (Lewu et al., 2019). Some of the products from cocoyam are cocoyam chips, flour and porridge. Cocoyam is affordable and helps in reducing the malnutrition in rural area in Nigeria. However, cocoyam has high water content and so, it is susceptible to deterioration; and therefore requires effective drying for its preservation (Afolabi et al., 2014). THEORY Usually, to obtain moisture content of a material, the material bone dry mass need to be known. Thus, at bone dry mass, a certain percentage of water which is the maximum allowable evaporated water has to be given off. The moisture content obtained at this point for freshly harvested materials of mass (Msy) is the maximum percentage of moisture content of the material. The initial mass of the material (Mim) immediately after harvesting is equal to Msy Equation (7) is a model and Q value may be termed as drying constant. The value of Q for any material whose freshly harvested mass is known could be obtained by plotting MC (wb) against to have Q as the slope of the graph. Thus, when the drying constants are known for materials, it is easy to predict the moisture content of such freshly harvested product once the mass of the material at any time is obtained. METHOD Freshly harvested roots and tubers such as yellow cassava, carrot, cocoyam and yam were sourced, then cleaned, sorted and cut into three masses classified as small, medium and large ; and then weighed. These mass classifications were subjected to drying at temperature of 70 0C, except carrot at 55 0C using a convectional hot oven until bone dry mass was obtained. The experimental values obtained were then computed to obtained moisture content (weight basis) and the corresponding ratio of initial mass at time t = 0 of the freshly harvested material to the mass at any time (t) during the drying period. A plot of MC versus based on (7) was carried out and the slope of the graph obtained as value of Q. Thus, value of Q was now substituted into the model (7). The model was now tested for validity and thereafter employed for freshly harvested materials in order to predict moisture content of the material, once the mass at any given time (t) during drying is known. RESULTS AND DISCUSSION A.Determination of Drying Constant of Yellow Cassava A temperature of 70°C was used to dry yellow cassava till a constant mass was obtained. Changes in moisture content per unit time were computed and plots of moisture content per unit time are given in Fig. (1) and (2). Now, let Q be a certain fraction that represent the maximum possible evaporated water in the material; and would result in obtaining a final mass (Mfm) (Antia et al., 2014). Mfm = Q Msy (1) Based on basic drying principles, material moisture content (MC) dry basis (db) or wet basis (wb) is given as: MC (wb) = Fig.1: Variation of moisture content against drying time for the different mass classifications of yellow cassava. (2) MC (db) = (3) The percentage of moisture content wet basis can be re- written as: % MC (wb) = × 100 (4) % MC (wb) = × 100 (5) % MC (wb) = × 100 (6) MC (wb) = (7) Fig. 2: Variation of moisture content against drying time for the bulk yellow cassava. @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 718

3. International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470 All the curves exhibit a falling rate period. The moisture content of each sample mass classification decreased with increase in drying time. Also, drying time increased with increase in mass classifications which implies that drying time is also dependent on mass classifications of the sample. The plots of drying rate versus drying time for each mass classification and bulk sample are given in Fig. (3) and (4) respectively. The slopes of the graphs which are equivalent to the drying constants were 0.3436, 0.2998, 0.2952, and 0.3114 0.0268 for small, medium, large and bulk yellow cassava respectively. B.Determination of Drying Constant of Carrot Fig. (7) and (8) show the variation of moisture content against drying time for the various mass classificationsof carrot dried at 55°C till constant mass was achieved. Fig. 3: Drying rate against drying time for the different mass classifications of yellow cassava. Fig.7: Variation of moisture content against drying time for the different mass classifications of carrot. Fig. 8: Variation of moisture content against drying time for the bulk carrot. Fig. 4: Drying rate against drying time for bulk yellow cassava. The moisture content of each classified sample mass decreased with increase in drying time. All the curves exhibit a falling rate period. The drying rate (DR) gotten per unit time for each mass classified and bulk sample are given in Fig. (9) and (10) respectively. The curves exhibit typical drying curves. Based on (7), Msy/Mim ratio was computed and standardized for the different mass classification. Plots of moisture content, wet basis (MC [wb]) are presented in Fig. (5) and (6). Fig. 5: Moisture content against Msy/Mim for the differentmass classifications of yellow cassava. Fig. 9: Drying rate against drying time for the different mass classifications of carrot. Fig. 6: Moisture content against Msy/Mimfor bulk yellow cassava. Fig. 10: Drying rate against drying time for bulk carrot. @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 719

4. International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470 The drying curve obtained is similar to ideal drying curve. The values of moisture content and Msy/Mim based on model (7) for the different mass classifications of the samples are given in Fig. (11) and (12). The moisture content of each classified sample mass decreased per unit time. The drying curve obtained is similar to an ideal drying curve. The drying rate for all the cocoyam mass classificationsdecreased with increase in drying time. The drying rates (DR) gotten per unit time for each classified mass are given in Fig. (15) and (16). Fig. 11: Moisture content against Msy/Mim for the different mass classifications of carrot. Fig.15: Drying rate against drying time for the different mass classifications of cocoyam. Fig. 12: Moisture content against Msy/Mim for bulk carrot. Fig.16: Drying rate against drying time for bulk cocoyam. The drying constants of small, medium, large and bulk carrot are 0.1229, 0.0995, 0.1131 and 0.1092 respectively. 0.0122 Moisture content and Msy/Mim values were computed and the plots of moisture content against Msy/Mim are shown in Fig.(17) and (18). C.Determination of Drying Constant of Cocoyam Fig. (13) and (14) show the changes in moisture content per drying time for all the mass classificationsof cocoyam dried at 70°C. Fig.17: Moisture content against Msy/Mim for the different mass classifications of cocoyam. Fig. 13: Variation of moisture content against drying time for the different mass classifications of cocoyam. Fig.18: Moisture content against Msy /Mim for bulk cocoyam. The drying constant for the small, medium, large and bulk cocoyam are 0.3945, 0.4477, 0.3066, and 0.3736 respectively. Fig. 14: Variation of moisture content against drying time for the bulk cocoyam. @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 720

5. International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470 Determination of Drying Constant of Yam Fig. (19) and (20) show the variation of moisture content against drying time for the various mass classificationsof yam dried till bone dry mass at 70°C. Fig.22: Drying rate against drying time for bulk yam. The plots of MC against Msy/Mim are presented in Fig. (23 and 24). Fig. 19: Variation of moisture content against drying time for the different mass classifications of yam. Fig.23: Moisture content against Msy/Mimfor the different mass classifications of yam. Fig. 20: Variation of moisture content against drying time for the yam. The moisture content of each classified sample mass decreased with increase in drying time. The drying curve obtained is similar to an ideal drying curve. The drying rate for all the classified yam masses decreased with increase in drying time as shown in Fig. (21) and (22). Figure 24: Moisture content against Msy /Mim for bulk yam. The slope of the graph is equivalent to the drying constant of the model (7). The drying constant for the small, medium, large and bulk samples were 0.3714, 0.3780, 0.3964, and 0.379 respectively. In summary, the drying constants for yellow cassava, carrot, cocoyam and yam are presented in Table 1. Fig. 21: Drying rate against drying time for the different mass classifications yam. TABLE 1: DRYING CONSTANTS FOR DIFFERENT SAMPLE SIZE RANGES AND THEIR STANDARD DEVIATIONS. Sample Mass Classification Mean (Bulk f) Deviation, d = x - mean Standard Deviation Sample Drying Constant (f) Variance Small Medium Large Small Medium Large Small Medium Large Small Medium Large 0.3436 0.2998 0.2952 0.1229 0.0995 0.1131 0.3945 0.4477 0.3066 0.3714 0.3780 0.3964 0.3114 0.3114 0.3114 0.1092 0.1092 0.1092 0.3736 0.3736 0.3736 0.3790 0.3790 0.3790 0.0322 -0.0116 -0.0162 0.0137 -0.0097 0.0039 0.0209 0.0741 -0.0670 -0.0076 -0.0010 0.0174 Yellow cassava 0.0007 0.0268 Carrot 0.0001 0.0122 Cocoyam 0.0052 0.0722 Yam 0.0002 0.0134 @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 721

6. International Journal of Trend in Scientific Research and Development (IJTSRD) @ www.ijtsrd.com eISSN: 2456-6470 [7]Doymaz, I. “Air-drying characteristics of tomatoes.” Journal of Food Engineering, 78(4), pp.1291–1297, 2007. PRACTICAL APPLICATION The (7) could be employed to know when to stop drying based on the mass of material predicted with respect to any desired moisture content during drying; once the initial mass of freshly harvested material is known. CONCLUSION The model (7) is useful in predicting moisture content of material at any time (t) during drying. The yellow cassava, carrot, cocoyam and yam have values of their drying constant as presented in Table 1. REFERENCES [1]T. J. Afolabi and T. Y. Tunde-Akintunde, “Effect of drying conditions on energy utilization during cocoyam drying,” Agric Eng Int: CIGR Journal, 16(4), pp.135－145, 2014. [8]M. K. Hazarika, and A. K. Datta, “Estimation of drying rate constant from static bed moisture profile by neural network inversion” Agric. Eng. Int.: CIGR Journal, 16(1), pp. 254-264, 2014. [9]D. Hosain, B. Ahmad, and Z. Mohammad, “Mathematical modeling and thin layer drying kinetics of carrot slices.” Global Journal of Science Frontier Research Mathematics and Decision Sciences, 12(7), 2012. [10]I. Ihekoronye, and O. Ngoddy, “Integrated food science and technology for the tropics.” London: Macmillan Press; [Google Scholar], 386p, 1985. [11]M.N. Lewu, P. O. Adebola, and A. J. Afolayan, “Effect of cooking on the proximate composition of the leaves of some accessions of Colocasia esculenta (L.) Schott in Kwa Zulu Natal province of South Africa.” African Journal of Biotechnology, 8(8),pp.1619-1622, 2009. [2]A. N. Agiriga, and M. O Iwe, “ Drying rate of selected varieties of cassava at different time of harvest-a response surface study.”British Journal of Applied Science & Techn., 13(5), pp.1-12, 2015. [12]A. Sifferlin, A. (2018). "Eat This Now: Rainbow Carrots". (Retrieved 29th August, 2018) [3]W. B. Akanbi, O. S. Olabode, J. O. Olaniyi and A.O. Ojo, “Introductionto tropical crops”. Ibadan: Raflink, pp,15– 20, 2004. [13]E. I. Uwem, O. O. Innocent, and R. E. Benjamin, (2018). “Kinetic models for drying techniques- food materials.” Scientific Research, 8 (2),pp. 27- 48, 2018. [4]O. Antia, O. Kessington, E. Aluyor, and P. Ebunilo “Study of moisture content dynamic of fresh palm nuts during drying,” International Journal of Engineering Science Invention, 3 (2), pp.19-23, 2014. [14]L. Uyigue, and M. A. Achadu, “Measurement and modeling of the thin Layer drying properties of selected varieties of yam assisted by hot-water blanching.” International Journal of Engineering and Modern Technology. 4(1):35-53, 2018. [5]O.O. Antia, and U. E. Assian, and O. William, “Modeling of water absorption by dried palm nut soaked at room temperature.” International Journal of Trend in Scientific Research and Development (IJTSRD),3 (3), pp.1499-1504, 2019c. [15]A. Westby,“Cassava utilization, storage and small scale processing.” CAB International; 2002. Cassava: Biology, Production and Utilization, pp. 281-300, 2002. https://www.academia.edu (Accessed on 25th Sept., 2018). [6]Doymaz, I. “Convective air drying characteristics of thin layer carrots.”Journal Engineering,61(3),pp.359-364, 2004. of Food @ IJTSRD | Unique Paper ID - IJTSRD23916 | Volume – 3 | Issue – 4 | May-Jun 2019 Page: 722